Polyarylensulfide, polyarylensulfide resin composition, method for producing polyarylensulfide

ABSTRACT

Provided are a polyarylene sulfide having a chloroform soluble content of at most 0.5% by weight and having an inherent viscosity ηinh of from 0.05 to 0.4; a polyarylene sulfide resin composition comprising a polyarylene sulfide and an inorganic filler, of which the chloroform soluble content is at most 0.5% by weight relative to the polyarylene sulfide in the composition; car parts produced through injection molding of the composition; and a method for producing a polyarylene sulfide. The polyarylene sulfide has a reduced content of low-molecular components, and has well balanced properties of fluidity, flexural strength and impact resistance.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a novel polyarylene sulfide, apolyarylene sulfide resin composition comprising it, injection moldingsof the composition, and a method for producing the polyarylene sulfide.Precisely, the invention relates to a resin composition comprising apolyarylene sulfide and glass fibers, of which the chloroform solublecontent is at most 0.5% by weight and which therefore has much balancedproperties of fluidity, flexural strength and impact resistance, andalso to injection moldings of the composition for car parts Further, theinvention relates to a novel polyarylene sulfide in which the content oflow-molecular-weight components is reduced, and to a method forproducing it.

[0003] 2. Description of the Related Art

[0004] Polyphenylene sulfide is a typical one of polyarylene sulfides,and is much used for parts for cars and electric and electronicappliances, as having the advantages of good heat resistance, flameretardancy, rigidity, solvent resistance and electric insulation.

[0005] However, for parts to be used in severe conditions, for example,for those for car engines, conventional resin compositions comprising acomposite of polyphenylene sulfide with glass fibers are still defectivein mechanical strength.

[0006] One known means for overcoming the problem is to increase themolecular weight of polyphenylene sulfide for enhancing the mechanicalstrength of the resin compositions. In this case, however, the fluidityof the resin compositions is lowered and therefore the moldabilitythereof is degraded. Given that situation, it is desired to develop sometechnique for enhancing the mechanical strength of the resincompositions without lowering the fluidity thereof.

SUMMARY OF THE INVENTION

[0007] The present invention has its object to provide a polyarylenesulfide resin composition having well balanced mechanical strength withits fluidity being not reduced, and its injection moldings, and also toprovide a novel polyarylene sulfide in which the content oflow-molecular-weight components is reduced, and a method for producingit.

[0008] We, the present inventors have assiduously studied the subjectmatter as above, and, as a result, have completed the invention which isas follows:

[0009] [1] A polyarylene sulfide resin composition comprising (A) from30 to 80% by weight of a polyarylene sulfide and (B) from 20 to 70% byweight of an inorganic filler, of which the chloroform soluble contentis at most 0.5% by weight relative to the polyarylene sulfide in thecomposition.

[0010] [2] Car parts as produced through injection molding of thepolyarylene sulfide resin composition of [1].

[0011] [3] A polyarylene sulfide having a chloroform soluble content ofat most 0.5% by weight and having an inherent viscosity, ηinh, of from0.05 to 0.4.

[0012] [4] A method for producing a polyarylene sulfide by reacting adihalogenoaromatic compound with lithium sulfide in an aprotic organicsolvent, which is characterized by adding from 21 to 100 mol %, relativeto the starting lithium sulfide, of lithium hydroxide to the reactionsystem.

[0013] [5] The method for producing a polyarylene sulfide of [4], whichis characterized by two-stage polymerization comprising aprepolymerization step of putting a part of the necessary amount of thestarting dihalogenoaromatic compound into the reaction system and afinal polycondensation step of adding the remaining part of the startingdihalogenoaromatic compound to the reaction mixture that contains theprepolymer formed in the previous step, or by multi-stage polymerizationof repeating the two steps.

[0014] [6] A method for producing a polyarylene sulfide by putting asulfur compound and a dihalogenoaromatic compound into a mixturecontaining lithium hydroxide in an aprotic organic solvent, whichcomprises;

[0015] (a) a step of putting a liquid or gaseous sulfur compound into amixture containing lithium hydroxide in an aprotic organic solvent tolead direct reaction between the sulfur compound and lithium hydroxide,

[0016] (b) a step of controlling the sulfur content of the resultingreaction mixture,

[0017] (c) a step of controlling the lithium hydroxide content of thereaction mixture to fall between 21 and 100 mol % of lithium sulfidetherein, and

[0018] (d) a step of putting a dihalogenoaromatic compound into thereaction mixture to lead polycondensation of the compound.

[0019] [7] The method for producing a polyarylene sulfide of [6], whichis characterized by two-stage polymerization comprising (e1) aprepolymerization step of putting the starting dihalogenoaromaticcompound into the reaction mixture and (e2) a final polycondensationstep of further putting the starting dihalogenoaromatic compound intothe reaction mixture that contains the prepolymer formed in the previousstep, or by multi-stage polymerization of repeating the two steps.

DETAILED DESCRIPTION OF THE INVENTION

[0020] Embodiments of the invention are described below.

[0021] Polyarylene Sulfide Resin Composition:

[0022] One aspect of the invention is to provide a polyarylene sulfideresin composition comprising (A) from 30 to 80% by weight, preferablyfrom 50 to 70% by weight, more preferably from 55 to 65% by weight of apolyarylene sulfide and (B) from 20 to 70% by weight, preferably from 30to 50% by weight, more preferably from 35 to 45% by weight of aninorganic filler, of which the chloroform soluble content is at most0.5% by weight, preferably at most 0.4% by weight, more preferably atmost 0.3% by weight relative to the polyarylene sulfide in thecomposition.

[0023] In the composition, if the amount of the inorganic filler islarger than 70% by weight, the fluidity of the composition is reduced;but if smaller than 20% by weight, the dimension stability of thecomposition is degraded. Preferably, the resin composition contains acoupling agent. Where the inorganic filler to be in the resincomposition is previously subjected to coupling treatment, the amount ofthe coupling agent to be added to the resin composition may be suitablydetermined depending on the degree of the pre-coupling treatment of theinorganic filler. If the pre-coupling treatment of the inorganic filleris satisfactory, any additional coupling agent will be unnecessary forthe resin composition. However, when the inorganic filler is anon-treated one, from 0.1 to 3.0 parts by weight, relative to 100 partsby weight of the polyarylene sulfide resin (A) in the composition, of acoupling agent maybe added to the composition.

[0024] Too much coupling agent over 3.0 parts by weight, if added to theresin composition, will cancel the capabilities of the inorganic fillerin the composition. On the other hand, however, if the amount of thecoupling agent added is smaller than 0.1 parts by weight, the mechanicalstrength of the composition will be reduced. If the chloroform solublecontent of the resin composition that contains an inorganic filler islarger than 0.5% by weight, the balance of fluidity and mechanicalstrength of the composition is poor.

[0025] The inorganic filler for use in the invention includes, forexample, glass fibers, carbon fibers, aramide fibers, potassium titanatewhiskers, silicon carbide whiskers, mica ceramic fibers, wollastonite,mica, talc, silica, alumina, kaolin, clay, silica-alumina, carbon black,calcium carbonate, titanium oxide, lithium carbonate, molybdenumdisulfide, graphite, iron oxide, glass beads, calcium phosphate, calciumsulfate, magnesium carbonate, magnesium phosphate, silicon nitride,hydrotalcite, etc. One or more of these inorganic fillers may be usedeither singly or as combined. Of those, especially preferred are glassfibers.

[0026] Glass fibers for use in the invention are not specificallydefined, and may be any of alkali glass, low-alkali glass or non-alkaliglass fibers. The fiber length preferably falls between 0.1 and 8 mm,more preferably between 0.3 and 6 mm; and the fiber diameter preferablyfalls between 0.1 and 30 μm, more preferably between 0.5 and 25 μm. Ifthe fiber length is smaller than 0.1 mm, the reinforcing effect of theglass fibers will be poor; but if larger than 8 mm, the fluidity of theresin composition containing such long glass fibers will be poor. If thefiber diameter is smaller than 0.1 μm, the fluidity of the resincomposition containing such thin glass fibers will be poor; but iflarger than 30 μm, the strength of the resin composition containing suchthick glass fibers will be low. The morphology of the glass fibers foruse herein is not also specifically defined. Various types of glassfibers are employable herein, including, for example, rovings, milledfibers, chopped strands, etc. One or more different types of glassfibers are used herein either singly or as combined.

[0027] For improving their affinity for resin, the glass fibers for useherein may be subjected to surface treatment with any of silane-typecoupling agents such as aminosilane-type, epoxysilane-type,vinylsilane-type or methacrylsilane-type coupling agents, ortitanate-type coupling agents such as tetramethyl orthotitanate-type ortetraethyl orthotitanate-type coupling agents, or chromium complexes orboron compounds.

[0028] As so mentioned hereinabove, any of the coupling agents notedabove may be separately added to the resin composition, in place ofsurface treatment of the glass fibers therewith.

[0029] If desired, any of weather-proofing agents, ultravioletabsorbents, antioxidants, lubricants, antistatic agents, flameretardants and other additives may be added to the resin composition ofthe invention to such an extent that they do not detract from theproperties of the composition. To produce the resin composition of theinvention, a polyarylene sulfide resin and an inorganic filler areblended in the defined ratio as above, and kneaded, for example, in aribbon tumbler, a Henschel mixer, a Banbury mixer, a drum tumbler, asingle-screw extruder or the like. The temperature at which they arekneaded generally falls between 280 and 320° C.

[0030] Use:

[0031] The polyarylene sulfide resin of the invention has the advantageof good balance between fluidity and mechanical strength, and can bemolded into thin-walled and complicated moldings. The moldings arefavorable to car parts, especially those for engines, and also toradiator parts, caps, hose clips, wiring connectors and others that arerequired to have high strength at high temperatures.

[0032] Polyarylene Sulfide:

[0033] The novel polyarylene sulfide of the invention has a chloroformsoluble content of at most 0.5% by weight, preferably at most 0.4% byweight, more preferably at most 0.3% by weight, and has an inherentviscosity, ηinh, of from 0.05 to 0.4, preferably from 0.10 to 0.35.

[0034] Since the amount of low-molecular-weight components therein issmall, the polyarylene sulfide has high flexural strength and highimpact resistance, and its fluidity is not reduced. When the polyarylenesulfide is combined with glass fibers, the resulting resin compositionexhibits well-balanced physical properties which conventional resincompositions could not.

[0035] If the chloroform soluble content of the polyarylene sulfide islarger than 0.5% by weight, the balance of fluidity and mechanicalstrength of the resin is poor.

[0036] If the inherent viscosity, ηinh, of the polyarylene sulfide issmaller than 0.05, the mechanical strength of the resin will be low; butif larger than 0.4, the moldability of the resin will be poor. Thepolyarylene sulfide of the a invention is a polymer having repetitiveunits of a structural formula, [—Ar—S—] wherein Ar indicates an arylenegroup and S indicates sulfur, in an amount of at least 70 mol %.Typically, it has repetitive units of the following chemical formula(I), in an amount of at least 70 mol %.

[0037] wherein R indicates a substituent selected from an alkyl oralkoxy group having at most 6 carbon atoms, a phenyl group, a carboxylgroup or its metal salt, a nitro group, or a halogen atom includingfluorine, chlorine and bromine atoms; and m indicates an integer of from0 to 4.

[0038] If the ratio of the repetitive units in the resin is smaller than70 mol %, the amount of the intrinsic crystalline componentcharacteristic of crystalline polymer in the resin will be small. If so,the mechanical strength of the resin will be poor.

[0039] The polyarylene sulfide may be not only a homopolymer but also acopolymer.

[0040] The comonomer units for the copolymer polyarylene sulfideinclude, for example, metaphenylene sulfide units, orthophenylenesulfide units, p,p′-diphenyleneketone sulfide units,p,p′-diphenylenesulfone sulfide units, p,p′-biphenylene sulfide units,p,p′-diphenylenemethylene sulfide units, p, p′-diphenylenecumenylsulfide units, naphthyl sulfide units, etc.

[0041] The polyarylene sulfide of the invention may be not only apolymer having a substantially linear structure but also a polymerhaving a branched structure or a crosslinked structure as formed throughpolymerization with a small amount of additional monomers having atleast 3 functional groups. If desired, the branched or crosslinkedpolymer may be blended with the polymer having a substantially linearstructure. Method for Producing Polyarylene Sulfide:

[0042] The invention also provides a novel method for producingpolyarylene sulfides, and this is one preferred embodiment of producingthe novel polyarylene sulfide of the invention noted above. The methodis characterized by adding a sulfur source and an additional chemical(alkali metal hydroxide) in a defined ratio to the polymerizationsystem. In the first aspect of the method, hydrogen sulfide gas or thelike is used as the sulfur source and a lithium compound is used as theadditional chemical serving for sulfur transfer and recovery.

[0043] We, the present applicant have clarified the basic principle ofthe method in our previous patent applications, Japanese PatentLaid-Open Nos. 343634/1993, 012215/1994, 044892/1994 and 076646/1994.

[0044] (I) First Aspect of Polymer Production Method:

[0045] The first aspect is a method for producing a polyarylene sulfideby putting a sulfur compound and a dihalogenoaromatic compound into amixture of lithium hydroxide and a solid substance except lithiumhydroxide in an aprotic organic solvent, which comprises:

[0046] (a) a step of putting a liquid or gaseous sulfur compound into amixture of lithium hydroxide and a solid substance except lithiumhydroxide in an aprotic organic solvent to thereby lead direct reactionbetween lithium hydroxide and the sulfur compound,

[0047] (b) a step of separating the solid substance except lithiumhydroxide,

[0048] (c) a step of controlling the sulfur content of the resultingreaction mixture,

[0049] (d) a step of controlling the lithium hydroxide content of thereaction mixture to fall between 21 and 100 mol % of lithium sulfidetherein,

[0050] (e) a step of putting a dihalogenoaromatic compound into thereaction mixture to lead polycondensation of the compound, and

[0051] (f) a step of putting an alkali metal hydroxide or an alkalineearth metal hydroxide into the reaction mixture which contains the sideproduct lithium chloride and from which the polycondensation productpolyarylene sulfide formed therein has been taken outside, thereby tolead reaction between lithium ions and hydroxyl ions, followed bycollecting the reaction product lithium hydroxide to recover lithiumions from the mixture.

[0052] The steps are described in detail hereinunder.

[0053] (1) Addition of sulfur compound (step (a)):

[0054] In the method of the invention, a liquid or gaseous sulfurcompound, for example, hydrogen sulfide gas is introduced into a mixturecontaining lithium hydroxide and a solid substance except lithiumhydroxide (e.g., sodium chloride) in an aprotic organic solvent, such asN-methyl-2-pyrrolidone (hereinafter referred to as NMP) to lead directreaction between lithium hydroxide and the sulfur compound. Through thereaction, lithium hydroxide is converted into lithium thiol (LiSH)soluble in NMP, whereby the NMP-insoluble, solid substance exceptlithium hydroxide (e.g., sodium chloride) is made separable from thereaction mixture. During the reaction, the temperature of the reactionsystem must be kept lower than 150° C. If the temperature is above 150°C., the NMP-soluble lithium thiol (LiSH) will be further converted intolithium sulfide (Li₂S) insoluble in NMP. If so, the NMP-insoluble, solidsubstance except lithium hydroxide (e.g., sodium chloride) could not beseparated from the reaction mixture.

[0055] The amount of the sulfur compound to be added may fall, in termsof the mol of the sulfur atom constituting the compound, between 0.5 and2 times the mol of lithium hydroxide added. If the amount is smallerthan 0.5 times mols, a part of lithium hydroxide will remain in thereaction mixture. On the other hand, even if a large amount of thesulfur compound over 2 times mols is added, the reaction will besaturated before the addition of such an excessive amount of the sulfurcompound. The sulfur compound is toxic, and excessively adding it isunfavorable.

[0056] As the sulfur compound to be used herein, preferred is hydrogensulfide gas. Hydrogen sulfide gas may be introduced into the mixtureeither under normal pressure or under elevated pressure. The time forthe gas introduction may fall generally between 10 and 180 minutes orso. The gas flow rate may fall generally between 10 and 1000 cc/min orso. For the gas introduction, for example, generally employed is amethod of bubbling the gas into the mixture of lithium hydroxide and asolid substance except lithium hydroxide (e.g., sodium chloride) in NMPwith the mixture being stirred.

[0057] The aprotic organic solvent to be used herein is generallyselected from aprotic polar organic compounds (e.g., amide compounds,lactam compounds, urea compounds, organic sulfur compounds, organiccyclic phosphorus compounds, etc.). A single solvent or a mixed solventof those compounds may be used herein.

[0058] Concretely, the amide compounds include N,N-dimethylformamide,N,N-diethylformamide, N,N-dimethylacetamide, etc.

[0059] The lactam compounds include caprolactam; N-alkylcaprolactamssuch as N-methylcaprolactam, N-ethylcaprolactam, etc.; and alsoN-methyl-2-pyrrolidone (NMP), N-ethyl-2-pyrrolidone,N-isopropyl-2-pyrrolidone, etc.

[0060] The urea compounds include tetramethylurea,N,N′-dimethylethyleneurea, etc.

[0061] The organic sulfur compounds include dimethyl sulfoxide, diethylsulfoxide, diphenyl sulfone, 1-methyl-1-oxosulfolane, etc.

[0062] The organic cyclic phosphorus compounds include1-methyl-1-oxophospholane, 1-n-propyl-1-oxophospholane,1-phenyl-1-oxophospholane, etc.

[0063] Of the aprotic organic solvents mentioned above, preferred areN-alkylcaprolactams and N-alkylpyrrolidones; and more preferred isN-methyl-2-pyrrolidone.

[0064] The solid substance except lithium hydroxide for use herein ismeant to indicate a solid substance excluding lithium hydroxide, andthis includes, for example, alkali metal chlorides and alkaline earthmetal chlorides such as sodium chloride, calcium chloride, magnesiumchloride, barium chloride, etc.

[0065] The solid substance except lithium hydroxide, which is separablein this step, is any of those alkali metal chlorides and alkaline earthmetal chlorides, such as sodium chloride, etc.

[0066] (2) Separation of solid substance except lithium hydroxide (step(b)):

[0067] In the previous step, a sulfur compound is put into the mixture,whereby the NMP-insoluble lithium hydroxide existing in the mixture isconverted into NMP-soluble lithium thiol (LiSH). As a result, the solidsubstance except lithium hydroxide (e.g., sodium chloride), which isinsoluble in NMP and which exists in the mixture, becomes separable fromthe mixture.

[0068] To separate it, employable are any known means of filtrationthrough a glass filter G4, centrifugation or the like. In the step forseparating it, the temperature of the mixture may fall generally between20 and 150° C.

[0069] (3) Control of sulfur content (step (c)):

[0070] In this step, the reaction mixture from which the solid substanceexcept lithium hydroxide (e.g., sodium chloride) has been separated issubjected to dehydrosulfurization to remove the excess sulfur componentfrom it, and, in addition, water having been produced as the sideproduct in the previous step of introducing hydrogen sulfide into themixture is also removed from it.

[0071] Precisely, in this step, the atomic ratio of sulfur/lithium inthe mixture is preferably controlled to be at most 1/2, more preferably1/2 in order to facilitate the next polymerization step with adihalogenoaromatic compound. If the atomic ratio is larger than 1/2, thepolymerization in the next step will be difficult. Regarding water thatmay exist in the polymerization step, a small amount of water willpromote the oligomerization in some degree in the former stage, and willeffectively function as a phase-separating agent in the latter finalpolymerization to increase the molecular weight of the oligomer formedin the former-stage oligomerization. However, both in the former andlatter stages, too much water is unfavorable. This is because water (inNMP) will often expel the oligomer from NMP, thereby retarding thepolymerization of the oligomer. For these reasons, therefore, it isdesirable that the amount of water existing in the reaction mixture iscontrolled to fall between 10 and 200% of lithium hydroxide in themixture.

[0072] For controlling the sulfur content and the water content of thereaction mixture, effectively employed is a method of bubbling nitrogeninto the reaction mixture under heat to thereby remove sulfur and waterfrom the mixture. In general, when the reaction mixture is heated at atemperature falling between 160 and 200° C., NMP-soluble lithium thiol(LiSH) is converted into NMP-insoluble lithium sulfide (Li₂S) whilegiving hydrogen sulfide.

[0073] (4) Control of lithium hydroxide content (step (d)):

[0074] In this step, the amount of lithium hydroxide to be present inthe reaction mixture is controlled to fall between 21 and 100 mol % oflithium sulfide (Li₂S) having been formed in the mixture.

[0075] Specifically, in the method of the invention, lithium hydroxidemust be present in the reaction system comprising a startingdihalogenoaromatic compound and a direct sulfur source of lithiumsulfide (Li₂S) that are necessary for the intended polycondensation, andits amount is controlled to fall between 21 and 100 mol %, preferablybetween 24 and 88 mol %, more preferably between 26 and 60 mol % of thesulfur source, lithium sulfide (Li₂S).

[0076] If the amount of lithium hydroxide existing in the reactionsystem is smaller than 21 mol %, it is difficult to control thechloroform soluble content of the final product, polyarylene sulfide tobe at most 0.5% by weight. If so, the polymer could not havewell-balanced fluidity and mechanical strength. On the other hand, evenif the amount of lithium hydroxide existing in the reaction system islarger than 100 mol %, any further improvement in the property balanceof the polymer could no more be expected.

[0077] This step is the most important part of the method of theinvention. Though not clear, the reason will be because aromatic —SLimoieties capable of being easily polymerized into high-molecular-weightpolymer segments will be much formed in the presence of excess lithiumhydroxide while, on the other hand, forming aromatic —SH moieties thatare hardly polymerized into high-molecular-weight polymer segments willbe retarded in that condition. As a result, it is presumed that forminglow-molecular-weight components will be retarded in the method of theinvention.

[0078] (5) Polycondensation, post-treatment (step (e)):

[0079] In this step, a dihalogenoaromatic compound is put into thepreviously prepared reaction mixture that contains lithium sulfide andlithium hydroxide, and polycondensed therein to give a polymer. Thepolymer is separated and washed to be the intended polyarylene sulfide.

[0080] The dihalogenoaromatic compound to be used herein includes, forexample, p-dichlorobenzene, p-dibromobenzene, 2,5-dichlorotoluene,2,5-dibromotoluene, 2,5-dichloro-tert-butylbenzene,2,5-dibromo-tert-butylbenene, 2,5-dichlorobiphenyl, etc. Of thecompounds, preferred are those containing at least 50 mol % ofp-dichlorobenzene and/or p-dibromobenzene.

[0081] Not detracting from the effect of the invention, any othercomonomers and branching agents may be copolymerized with thedihalogenoaromatic compound. The comonomers include, for example,2,3-dichlorophenol, 2,3-dibromophenol, 2,4-dichlorophenol,2,4-dibromophenol, 2,5-dichlorophenol, 2,5-dibromophenol,2,4-dichloroaniline, 2,4-dibromoaniline, 2,5-dichloroaniline,2,5-dibromoaniline, 3,3′-dichloro-4,4′-diaminobiphenyl,3,3′-dibromo-4,4′-diaminobiphenyl, 3,3′-dichloro-4,4′-dihydroxybiphenyl,3,3′-dibromo-4,4′-dihydroxybiphenyl, di(3-chloro-4-amino)phenylmethane,m-dichlorobenzene, m-dibromobenzene, o-dichlorobenzene,o-dibromobenzene, 4,4′-dichlorodiphenyl ether, 4,4′-dichlorodiphenylsulfone, etc. The branching agents include, for example,1,2,4-trichlorobenzene, 1,3,5-trichlorobenzene, 1,2,3-trichlorobenzene,etc.

[0082] One or more of these comonomers and branching agents may beemployed herein, either singly or as combined.

[0083] The reactor for the polycondensation in this step may be, forexample, a stainless steel autoclave having a capacity of 1 liter. Thismay be equipped with a paddle stirrer capable of rotating at a speed offrom 300 to 700 rpm. The polymerization temperature preferably fallsbetween 220 and 260° C., and the polymerization time preferably fallsbetween 1 and 6 hours. The amount of the dihalogenoaromatic compound tobe put into the reaction mixture is preferably such that the ratio (bymol) of the dihalogenoaromatic compound to sulfur to be in the systemfalls between 0.9 and 1.2, more preferably between 0.95 and 1.05. If themolar ratio is smaller than 0.9, the molecular weight of the polymer tobe produced could not increase; and if larger than 1.2, the molecularweight thereof could not also increase.

[0084] The polymerization may be effected in one stage, or in two ormore stages for two-stage or multi-stage polymerization. In thetwo-stage polymerization, the monomers are prepolymerized in the formerstage, and the resulting prepolymer may be further polymerized into afinal polymer having an increased molecular weight. Preferred is thetwo-stage polymerization favorable to production of polymers ofdifferent polymerization grades. Regarding the polymerizationtemperature and time in the two-stage polymerization, the former-stageprepolymerization may be effected at relatively low temperatures fallingbetween 190 and 240° C. or so and will take 2 to 10 hours or so, and thelatter-stage final polymerization may be effected at relatively hightemperatures falling between 240 and 270° C. or so and will take 1 to 3hours or so. As the case may be, the water content in the reactionsystem will be controlled separately in the former and latter stages.

[0085] The polymer formed may be subjected to any ordinarypost-treatment. For example, the reaction system containing the polymerformed is cooled, and the precipitate formed therein is taken outthrough centrifugation, filtration or the like, and the thus-separatedpolymer is washed a few times with an organic solvent or water underheat or at room temperature to purify it. For washing it, the polymermay be solid or may be liquid. For the latter, the liquid polymer may bewashed in melt.

[0086] (6) Lithium ion recovery (step (f)):

[0087] In this step, an alkali metal hydroxide or an alkaline earthmetal hydroxide is put into the reaction mixture which contains lithiumchloride having been formed in the previous polycondensation step as theside product and dissolved in NMP and from which the product,polyarylene sulfide has been taken outside, thereby leading reactionbetween lithium ions and hydroxyl ions to give lithium hydroxide. Thethus-formed lithium hydroxide is collected.

[0088] The alkali metal hydroxide and the alkaline earth metal hydroxidefor use herein include, for example, sodium hydroxide, potassiumhydroxide, magnesium hydroxide, etc. Of those, preferred is sodiumhydroxide. The amount of the hydroxide compound to be put into thereaction mixture is controlled to fall between 0.9 and 1.1 mols,preferably between 0.95 and 1.05 mols, in terms of the hydroxyl grouprelative to one mol of the lithium ions existing in the mixture. If theamount is smaller than 0.9 mols, the lithium recovery will beinsufficient; but if larger than 1.1 mols, the purity of the product,polyarylene sulfide will lower in relation to the subsequent operation.The reaction temperature in this step is not specifically defined. Forexample, when an aqueous solution of an alkali metal or alkaline earthmetal hydroxide is put into the reaction mixture, the reactiontemperature may fall between room temperature and 230° C., preferablybetween 65 and 150° C.; but when a solid of the hydroxide is putthereinto, the reaction temperature may fall between 60 and 230° C.,preferably between 90 and 150° C. If the reaction temperature in thisstep is too low, the hydroxide compound added will be difficult todissolve in the mixture and the reaction speed will be extremely slow.On the other hand, if the reaction temperature is too high, it willabove the boiling point of NMP. In that case, the reaction must beeffected under elevated pressure, but such is unfavorable to theprocess. The reaction time is not specifically defined.

[0089] (II) Second Aspect of Polymer Production Method:

[0090] The second aspect of the polymer production method of theinvention is to produce a polyarylene sulfide in one-stage ormulti-stage polycondensation in which lithium sulfide and lithiumhydroxide are added to a dihalogenoaromatic compound in the presence ofan aprotic organic solvent. The method of polyarylene sulfide productionis characterized in that the amount of lithium hydroxide to be added tothe reaction system is controlled to fall between 21 and 100 mol % oflithium sulfide added thereto.

[0091] The second aspect differs from the first aspect in that thesulfur source to be added to the reaction system is lithium sulfide butnot hydrogen sulfide. In the second aspect, therefore, the lithium cycleis outside the reaction system. The other materials to be used and thereaction conditions in the second aspect are the same as those in thefirst aspect.

[0092] Specifically, in the second aspect, lithium sulfide is added to adihalogenoaromatic compound in a ratio (by mol) of dihalogenomaticcompound/lithium sulfide falling between 0.9 and 1.2, in the presence ofan aprotic organic solvent such as NMP or the like, while lithiumhydroxide is added thereto in an amount of from 21 to 100 mol % oflithium sulfide added. In this, preferred is two-stage polymerization.In the former stage, a part of the starting materials are put into thereactor to lead prepolymerization, and in the latter stage, theremaining parts of the starting materials and water are added to thereaction system so as to satisfy the ratio, water/lithium sulfidefalling between 0.1 and 2.5 by mol, thereby leading final polymerizationto give the final polymer having an increased molecular weight.Regarding the reaction conditions, the polymerization temperature mayfall between 190 and 240° C. in the former stage and between 240 and270° C. in the latter stage, and the polymerization time may fallbetween 2 and 10 hours in the former stage and between 1 and 3 hours inthe latter stage.

[0093] In the latter stage, lithium chloride is formed throughpolycondensation and dissolves in NMP. In this, when the lithiumchloride concentration in the presence of water (water is dissolved inNMP) increases, the polymer reaction mixture will undergo phaseseparation to give two phases of lithium chloride-NMP phase andpolymer-NMP phase. In that condition, the molecular weight of thepolymer formed is much increased.

[0094] After the reaction, the polymer formed may be post-treated in anyordinary manner. For example, the reaction system containing the polymerformed is cooled, and the precipitate formed therein is taken outthrough centrifugation, filtration or the like, and the thus-separatedpolymer is washed a few times with an organic solvent or water underheat or at room temperature to purify it.

[0095] The invention is described in more detail with reference to thefollowing Examples.

[0096] The test methods employed in Examples are mentioned below.Measurement of chloroform-soluble component:

[0097] Pellets as prepared through pelletization of a melt sample arecooled with liquid nitrogen, ground into powder, and sieved through a9-mesh sieve, and the resulting powder sample is subjected to Soxhletextraction with a solvent of chloroform for 8 hours. The resultingextract is filtered at a temperature not lower than 40° C. to remove thesolvent therefrom, and the resulting solid residue is measured. This isthe chloroform-soluble component of the sample. For the filtration, usedis a cylindrical paper filter of ADVANTEC 84 (28×100 mm). 9 g of thepowder sample is subjected to Soxhlet extraction. The chloroform-solublecomponent is represented by the ratio by weight (%) to the sample,polyarylene sulfide.

[0098] Spiral Flow Length:

[0099] Used is Toshiba Kikai's JS30EPN (this is a 30-toninjection-molding machine) equipped with a spiral flow mold for 1mm-thick sheets.

[0100] Concretely, a melt sample to be tested is injected into the moldunder an injection pressure of 1000 kgf/cm² (set pressure 49%), at asample temperature of 320° C. and at a mold temperature of 135° C., andis molded therein, for which the injection time is 10 seconds. Thelength (mm) of the sample flow having been injected in that condition ismeasured, and this indicates the spiral flow length of the sampletested.

[0101] Flexural Strength:

[0102] Used is a Nippon Steel Works' J750EP (this is a 50-toninjection-molding machine). Concretely, a sample to be tested ispress-molded at a sample temperature of 320° C. and at a moldtemperature of 135° C. into test pieces having a size of 127×12.7×3.18mm. The test pieces are measured according to ASTM-790. The unit is MPa.

[0103] Izod Impact Strength:

[0104] The same test pieces as those for the flexural strength test aretested for the Izod impact strength with no notch, according toASTM-D256. The unit is kJ/m².

[0105] Measurement of Inherent Viscosity:

[0106] 0.04 g±0.001 g of a polymer sample to be tested is dissolved in10 cc of α-chloronaphthalene at 235° C. within a period of 15 minutes,and kept in a thermostat at 206° C. The viscosity of the polymer samplesolution is measured and compared with the viscosity ofα-chloronaphthalene with no polymer sample therein to obtain therelative viscosity of the polymer sample.

[0107] The inherent viscosity ηihr of the sample is represented by thefollowing equation:

ηihr=ln(relative viscosity)/polymer concentration(dl/g)

EXAMPLE 1

[0108] 10 mols (459.4 g) of lithium sulfide, 9 mols (1323 g) ofp-dichlorobenzene, 0.5 mols (20.98 g) of lithium hydroxide monohydrate,and 4.2 liters of NMP (N-methyl-2-pyrrolidone) were put into anautoclave having a capacity of 10 liters, reacted at 200° C. for 5hours, and cooled to room temperature to obtain a prepolymer.

[0109] To the prepolymer, added were 1.0 mol (147.0 g) ofp-dichlorobenzene, 1.9 mols (79.73 g) of lithium hydroxide monohydrateand 9.0 mols (162.1 g) of water, and reacted at 260° C. for 3 hours.After cooled to 100° C., the liquid phase was separated, and the polymerdeposited was collected. The polymer was washed three times with coldwater.

[0110] The polymer was again put into an autoclave having a capacity of10 liters, to which were added 5 liters of NMP and 30 cc of acetic acid.The polymer was washed with these at 150° C. for 1 hour. After cooled,the solid polymer was washed with cold water until itselectroconductivity reached 20 μS/cm or less. After thus washed, thepolymer was dried in an air drier at 120° C. for 24 hours, and thenfurther dried in vacuum at 120° C. for 24 hours.

[0111] 60 parts by weight of the polymer, 40 parts by weight of glassfibers JAF591 (from Asahi Fiber Glass) and 1 part by weight of a silanecoupling agent SH6040 (from Toray Dow Corning) were blended in dry, andpelletized through extraction at 320° C. into pellets.

[0112] The pure polymer powder was tested for the inherent viscosity,and the composite resin pellets were tested for the chloroform solublecontent, the spiral flow length, the flexural strength and the Izodimpact strength. Based on the test data, the polymer was evaluated forits properties. The data are in Table 1 below.

EXAMPLE 2

[0113] The same process as in Example 1 was repeated, except that theamount of lithium hydroxide monohydrate to be added to the prepolymerwas varied from 1.9 mols (79.73 g) to 4.5 mols (188.8 g) and that ofwater to be added thereto was varied from 9.0 mols (162.1 g) to 5.0 mols(90.1 g). The test data are in Table 1.

EXAMPLE 3

[0114] 10 mols (459.4 g) of lithium sulfide, 10 mols (1470 g) ofp-dichlorobenzene, 3.5 mols (146.9 g) of lithium hydroxide monohydrate,6.0 mols (108.1 g) of water and 4.2 liters of NMP(N-methyl-2-pyrrolidone) were put into an autoclave having a capacity of10 liters, reacted at 260° C. for 3 hours. After cooled to 100° C., theliquid phase was separated, and the polymer deposited was collected.This was processed in the same manner as in Example 1. The test data arein Table 1.

EXAMPLE 4

[0115] Step of hydrogen sulfide addition:

[0116] 415.94 g (4.2 mols) of NMP (N-methyl-2-pyrrolidone), 123.5 g of amixture of LiOH and NaCl (1.5 mols each) and 27.0 g (1.5 mols) ofdeionized water were put into a 500 ml separable glass flask equippedwith a paddle stirrer, and heated up to 130° C.

[0117] After this was heated so, hydrogen sulfide was introducedthereinto at a flow rate of 700 ml/min for 35 minutes. In this step, theliquid temperature was all the time controlled to be at 130° C. duringthe hydrogen sulfide addition.

[0118] Adding hydrogen sulfide was stopped, and the S (sulfur)content ofthe liquid was determined. The liquid absorbed 1.65 mols of S, and theratio by mol of S/Li in the liquid was 1.1 The S (sulfur) content of theliquid was measured through iodometry. Briefly, diluted hydrochloricacid is added to a sample of the liquid, and an excess iodine solutionis added thereto, and this is subjected to back titration with astandard solution of sodium thiosulfate.

[0119] Step of NaCl Separation:

[0120] The liquid having been absorbed hydrogen sulfide was transferredonto a glass filter kept at 130° C., and filtered therethrough underreduced pressure. The reside remaining on the filter was washed with alarge amount of N-methyl-2-pyrrolidone at 130° C., and dried underreduced pressure at 150° C. The dried solid weighed 87.4 g. Its X-raydiffractiometry gave a spectrum of only NaCl and did not give a spectrumof LiOH.

[0121] From the result as above, it is understood that when hydrogensulfide is introduced into a mixture of LiOH and NaCl, it reacts withonly LiOH to give a complex soluble in N-methyl-2-pyrrolidone. In thisstep, therefore, the solid NaCl can be separated from the reactionmixture.

[0122] Step of Controlling Sulfur Content:

[0123] On the other hand, 400.0 g of the liquid having absorbed hydrogensulfide was transferred into a separable flask of the same type asabove, and heated up to 150° C., into which was introduced N₂ gas at aflow rate of 700 ml/min so as to expel the excess hydrogen sulfide fromthe liquid until the ratio by mol of S/Li in the liquid reached 0.50.

[0124] In that condition, N₂ gas was introduced into the liquid for 70minutes to attain the molar ratio S/Li of 0.50.

[0125] Step of Polycondensation and Post-Treatment:

[0126] The liquid having been thus controlled in the previous step wastransferred into a stainless steel autoclave having a capacity of 1liter, and 173.0 g of paradichlorobenzene (PDCB) was added thereto tohave a molar ratio, PDCB/S=1.00. Then, lithium hydroxide was addedthereto to have a molar ratio LiOH/Li=0.30, relative to Li in theliquid. This was heated up to 240° C. and kept at the elevatedtemperature for 30 minutes to lead precondensation of the monomers.Next, this was further heated up to 260° C., at which the resultingprepolymer was further polymerized for 3 hours. After cooled, thegranular polymer obtained was washed with pure water, substituted withacetone, and dried in a vacuum drier. The dry polymer weighed 119.5 g.It had an inherent viscosity ηihr of 0.34 dl/g. The inherent viscosityis an index of the molecular weight of the polymer.

[0127] 60 parts by weight of the powdery polymer obtained herein, 40parts by weight of glass fibers JAF591 (from Asahi Fiber Glass) and 1part by weight of a silane coupling agent SH6040 (from Toray DowCorning) were blended in dry, and pelletized through extraction at 320°C. into pellets.

[0128] The pure polymer powder was tested for the inherent viscosity,and the composite resin pellets were tested for the chloroform solublecontent, the spiral flow length, the flexural strength and the Izodimpact strength. Based on the test data, the polymer was evaluated forits properties. The data are in Table 1 below.

[0129] Step of Producing LiOH:

[0130] 415.94 g (4.2 mols) of N-methyl-2-pyrrolidone and 63.585 g (1.5mols) of lithium chloride were put into a 500 ml separable glass flaskequipped with a paddle stirrer, and lithium chloride was dissolved inthe solvent at 90° C. To the resulting solution, added was 125.0 g of 48wt. % sodium hydroxide solution (corresponding to 1.5 mols of NaOH).Immediately after the addition, a white solid was formed at a time. In anitrogen atmosphere, this was heated to remove the dissolved watertherefrom.

[0131] The dewatered mixture was cooled, and transferred onto a glassfilter (G4) at room temperature, through which the mixture was filteredunder reduced pressure. The residue remaining on the filter was dried at150° C. under reduced pressure. The dried solid weighed 123.5 g. Itselementary analysis gave data of Na/Li/Cl (by mol)=1.03/1.00/1.00. ItsX-ray diffractiometry gave spectral peaks for LiOH and NaCl. Through ionchromatography, neither lithium ions nor sodium ions were detected inthe supernatant layer (NMP layer) from the solid. From the analyticaldata as above, it is understood that LiCl and NaOH were almostcompletely (100%) converted into LiOH and NaCl.

COMPARATIVE EXAMPLE 1

[0132] The same process as in Example 1 was repeated, except thatlithium hydroxide monohydrate was not added to the prepolymer and thatthe amount of water to be added to the prepolymer was varied from 9.0mols (162.1 g) to 11 mols (198 g). The test data are in Table 1.

COMPARATIVE EXAMPLE 2

[0133] The same process as in Example 1 was repeated, except that theamount of lithium hydroxide monohydrate added to the prepolymer was 1.5mols (62.95 g) and that of water to be added thereto was varied from 9.0mols (162.1 g) to 10 mols (180 g). The test data are in Table 1.

COMPARATIVE EXAMPLE 3

[0134] The same process as in Example 3 was repeated, except that theamount of lithium hydroxide monohydrate was varied from 3.5 mols (146.9g) to 10 mols (419.6 g). The test data are in Table 1.

REFERENCE EXAMPLE

[0135] A commercial product, Fortlon 1140A6 (from Polyplastics; this isreinforced with 40% by weight of glass fibers) was tested for itsproperties. The test data are in Table 1. TABLE 1 Inherent ChloroformFlexural Izod Impact Viscosity Amount of LiOH Soluble Content SFLStrength Strength (dl/g) (mol %) (%) (mm) (MPa) (kJ/m²) Example 1 0.2124 0.42 167 314 76 Example 2 0.21 50 0.22 165 300 77 Example 3 0.21 350.23 168 301 78 Example 4 0.34 30 0.22  15 310 78 Comparative 0.21  50.60 165 289 59 Example 1 Comparative 0.21 20 0.54 168 288 57 Example 2Comparative 0.21 10 0.57 167 287 58 Example 3 Reference — — 0.87 156 27665 Example

[0136] As described above, the method of the invention producespolyarylene sulfides having a chloroform soluble content of not largerthan 0.5% by weight, in any mode of single-stage polymerization (as inExample 3) and two-stage polymerization (as in Examples 1 and 2).Accordingly, glass fiber-reinforced resin compositions of the inventionall have well-balanced properties of fluidity, flexural strength andIzod impact strength. As opposed to these, however, the chloroformsoluble content of the polymers produced in Comparative Examples 1, 2and 3, in which the blend ratio of lithium hydroxide monohydrate issmall, is large. Therefore, the balance of fluidity, flexural strengthand Izod impact strength of the glass fiber-reinforced resincompositions of those Comparative Examples is not good. On the otherhand, the inherent viscosity of the polymer of Example 4, for which isused hydrogen sulfide as the sulfur source, is high, and therefore thespiral flow length of the polymer composition is not long. However, thebalance of flexural strength and Izod impact strength of the polymercomposition of Example 4 is good. Compared with the resin composition ofReference Example, it is understood that the physical property balanceof the resin compositions of the invention is much improved.

What is claimed is:
 1. A polyarylene sulfide resin compositioncomprising (A) from 30 to 80% by weight of a polyarylene sulfide and (B)from 20 to 70% by weight of an inorganic filler, of which the chloroformsoluble content is at most 0.5% by weight relative to the polyarylenesulfide in the composition.
 2. Car parts as produced through injectionmolding of the polyarylene sulfide resin composition of claim
 1. 3. Apolyarylene sulfide having a chloroform soluble content of at most 0.5%by weight and having an inherent viscosity, ηinh, of from 0.05 to 0.4. 4A method for producing a polyarylene sulfide by reacting adihalogenoaromatic compound with lithium sulfide in an aprotic organicsolvent, which is characterized by adding from 21 to 100 mol %, relativeto the starting lithium sulfide, of lithium hydroxide to the reactionsystem.
 5. The method for producing a polyarylene sulfide as claimed inclaim 4, which is characterized by two-stage polymerization comprising aprepolymerization step of putting a part of the necessary amount of thestarting dihalogenoaromatic compound into the reaction system and afinal polycondensation step of adding the remaining part of the startingdihalogenoaromatic compound to the reaction mixture that contains theprepolymer formed in the previous step, or by multi-stage polymerizationof repeating the two steps.
 6. A method for producing a polyarylenesulfide by putting a sulfur compound and a dihalogenoaromatic compoundinto a mixture containing lithium hydroxide in an aprotic organicsolvent, which comprises; (a) a step of putting a liquid or gaseoussulfur compound into a mixture containing lithium hydroxide in anaprotic organic solvent to lead direct reaction between the sulfurcompound and lithium hydroxide, (b) a step of controlling the sulfurcontent of the resulting reaction mixture, (c) a step of controlling thelithium hydroxide content of the reaction mixture to fall between 21 and100 mol % of lithium sulfide therein, and (d) a step of putting adihalogenoaromatic compound into the reaction mixture to leadpolycondensation of the compound.
 7. The method for producing apolyarylene sulfide as claimed in claim 6, which is characterized bytwo-stage polymerization comprising (e1) a prepolymerization step ofputting the starting dihalogenoaromatic compound into the reactionmixture and (e2) a final polycondensation step of further putting thestarting dihalogenoaromatic compound into the reaction mixture thatcontains the prepolymer formed in the previous step, or by multi-stagepolymerization of repeating the two steps.